CHAPTER I
INTRODUCTION
1.1 Background
Bolt-nut joint, one of the joint structures is widely used as it’s easiness to install and remove, produces big fastening power with small force and low price in
production. Disadvantage of bolt-nut, when vibration and thermal load applied to the thread joint, bolt will lose and fastening became unsustainable. In FE method,
substitute for a simplified and accurate numerical model to predict load share on every joint. So, this method can investigated the results of the sliding and loosening
behaviour and bending moment at the bolt neck which are the critical relative slippage S
cr
and bending moment of bolt. There have 2 type of load acting which is tensile load and transverse load.
Tensile load is line of forces is parallel to axes of the bolt. Transverse load is line of action forces is perpendicular to the axes of the bolt. From other research, transverse
load loosen to the bolt-nut joint more than tensile load. The problem occurs is bolt-nut is model as unit and thread of bolt and nut do not
exist at the corresponding portion. This problem can simplify presume that relative between fastened plates. In order to predict the sliding behaviour and relative critical
slippage, consideration of clearance between bolt and nut thread surface must be made. The bending moment stress needs to be considered due to fatigue failure. The
new model must be considered both critical relative slippage and bending moment generated at the bolt neck.
The loosening behaviour of bolt-nut joint shows the same occurrence if the transverse load applied in the opposite direction. The axial tension will decrease
when transverse cyclic load applied to the joint. At the worst stage, fatigue failure also will occur.
In this project, firstly we present the equation for estimating the Scr based on the fundamental cantilever deformation model. Then we present the investigated results
of the deformation behaviour of bolt-nut joint under transverse loading condition considering the reaction moment by nut. Finally, we can confirm that these estimated
results of critical relative slippage coincided well with the experimental results.
1.2 Problem Statement
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